Polar communication system



April 20, 1954 M. L.. DoELz POLAR COMMUNICATION SYSTEM 6 Sheets-Sheet 1 Filed Dec.`2, 1949 lilzll YApril zo, 19,54 M L Dom 2,676,245

- POLAR COMMUNICATION SYSTEMA Filed Dec. 2, 1949 I 6 Sheets-Sheet 2 S S; m SS L *q a T) April 20, 1954 M. DoELz POLAR COMMUNICATION SYSTEM 6 Sheets-Sheet 3 Filed Dec. 2, 1949 NOSRSQ W; XS Q Su IIE Maf/Wap M f April 20, 1954 M. L. DoELz 2,676,245

POLAR COMMUNICATION SYSTEM u Filed Dec. 2, 1949 A 6 Sheets--SheetI 4 Anh A 1 I im-Wh O i" @Null-l Pn M. L. .DOELZ POLAR COMMUNICATION SYSTEM 6 Sheets-Sheet 5 Filed Dc. 2, 1949 mw NSQMG Mwmmk Q mh/ NQQONN /NVENTR fw April 20, 1954 M, L, DOELZ 2,676,245-

POLAR COMMUNICATION SYSTEM i Filed Deo. 2, 1949 6 Sheets-Sheet 6 Patented Apr. 20, 1954 UNITED" s'rA'rEs l PATIENT orificev Collins Radio Company,

corporation 4of Iowa Application December 2, 1949, Serial No. 130,810

l Thi-s invention relatesin general to radiant energy data transmission systems and in particular to a vpolar data transmission system.

YIn polarity-time transmission of data by wire it has long been realized `thatpolar transmission is superior to on-off transmission. In an on. off system the intelligence' to betransmitted'is encoded into pulses and spaces (lack of pulses). Because of ever present noise, the spaces are not 'always discernible and consequently errorsoccur in the .transmission o f the intelligence. In apolar system a pulse is sent during each timeinterval andthe' intelligence. is encoded into the .pulses by'reversi'ng-the polarityl of some of them. The Ymagnitude of the pulses remains Aconstant and it i-s only the'polarity which changes.Y VThe chance of error in the polar transmission system is much less thanr the on-off 'systemv vbecause nearly always the transmitted pulse is discernible through noise. The problem of establishing a polarity referencein a wired system is relatively simple, however, in a polar radiant energy system many difcultiesare encountered.

Vltfislanobject of the present invention, therefore, to provide 'a polar transmission system wherein a change inthe polarity of the signal corresponds to a mark in the data, and no change in ,polaritypof the signal corresponds to a space in thedata. Y f l A further object of this invention is to provide a radiant energy polar transmission system which requires only a narrow band width.

Yet another object of this invention is to provide a polar transmission system which can be cheaply and quickly constructed.

Further objects and advantages will appear in the specification and drawings. in which: Y

A Fig. l is a schematic diagram of the polar transmitter of this invention; i v Y,

Fig. 2 is a detailed wiring diagram of the phase reversingv circuit of the transmitter shown in Fig. 1;v v

Fig. 3 is a schematic diagram of the receiver of this invention; and A i Fig. 4 is a detailed wiring diagramof the'phase detecting vand reversing circuits of the receiver shown in Fig. 3; ,fr Fig. 5 is a wiring diagram of receiver shown in Fig. 3;

Fig.`6 is, an example of mark-spacev information which it is desired to transmit by thesystem of this information; Y

' Fig.' 7 illustrates 'the transmitted wave shape for the information illustrated in Fig. 5; j

Fig.l 'illustrates the output of phase detector almo'diflcation of 6 Claims. (Cl. Z50-8) A* work'I 2 receives the radio frequency I1 has modulated the carrier Cedar Rapids, Iowa, a

Fig. 9 illustrates vthe output of phase detector 48 when the phase of the local oscillator is reversed 180 degrees; and

Fig. l0 illustrates the output of the full wave rectifier 12.

vWith reference to the'drawings, Fig. lv illustrates a transmitter which has a crystal oscillator I6) which feeds a multiplier VII to obtain a radio frequency carrier wave.l A` phase reversing netcarrier from the multiplier II and reverses the phase. of the carrierjby 180 degrees in response to data impulses furnished to a controlling trigger circuit I3. A power amplier I4 receives the output of the phase `reversing network I2 rand ampliiies it before supplying a radiating antenna I6l with the rcarrier.

The modulator Il produces a modulating signal with a frequency equal'to the frequency of transnmissionof pulses. The modulating signal modulates the carrier wave in the power amplifier I4. The modulationis 100 per cent so that the carrier wave goes to zero each cycle of the modulating wave.

The modulation is in synchronism with the data pulses'V furnished by the information source I8. Thus, the trigger circuit I3y causes the phase reversing network to reverse-'the phase4 of the radio frequency carrier at a time when the modulator to zero. Thus if there is a .phase reversal noextreme transient effect will occur. For a more detailed explanation of the manner in whichtthe modulator I1 may be Ysynchronized with the data. pulses from the inhformation source I8 reference may be made to page 497, Proceedings of I. R. E., volume 37 (May 1949) vReferring to Fig. 2, the phase reversing network I2 and'l trigger circuit I3 are shown in more detail. A' pair of vacuum tube amplifiers I9 and 2l f are driven in phase by the radio frequency signal from the multiplier I I. The cathodes 22 and 23 are connected together and the plates 24 and 23 areY connected to opposite ends of a tank circuit 21. Thus, if provision is made 'for only one of the tubes I9 or 2l to conduct ata time, the output across the tank 21 will reverse phase `by 180 degrees whenrcond'uction changes from onevtube to the other. i

The trigger circuit I 3 comprises the two tubes 28 and 29 'connected with their cathodes 3| and 32 together and may be of the well-known Eccles- Jordan type. The plates 33 and 34of thetubes 28 and 29 areyconne'cted'to the grids 36 vand 31 of the phase reversing network I2. Thus when plate current owsin tube 28. tube 2q is biased past cut-on and current will now in tube I9. When tube 29 of the trigger circuit is conducting, tube 28 is biased past cut-olf and, consequently, current Will flow in tube 2|.

The Eccles-Jordan circuit has only two stable conditions, to Wit:

1. Plate curr-ent flowing in tube 28 and no plate current in tube 29; and

2. Plate current flowing in tube 29 and no plate current in tube 28.

The grid 38 of tube 28 is connected in series with resistors 39 and 4l to grid l42. A-triggering signal is furnished to the gridcircuit from the information source I8 at thepoint 43 and when the triggering signal is suiciently negative the trigger circuit will go from one stable condition to the other.

device in Voscillator 49 in `such fa manner that the oscillator obtains a phase lock, the output of oscillator 49 will be at the same frequency as the signal from amplier 41. Since the outputfrom the -100 kc. I. F. amplifier 41 is multiplied by two before being fed to phase detector 54, a signal appearing at 54 is identical for either polarity of the signal from the I. F. amplifier 41 and, if the oscillator 49 is in phase with reither-of the twoltypes of incoming waves, zero The information source supplies negativepulses to the trigger circuit I3. The information source may be, for example, a teletype .machine capable of coding written intelligence into an on-oit code. That is, on indicates a mark and olf indicates a space Now if all marks are negative pulses, it will be seen that the trigger vcircuit I3 will go from one stable condition to .the other when a mark is sent by the information source. Likewise, the trigger circuit will remain inthe prior stable condition when a space is sent. Stated otherwise, the presence oi' a .negative pulse indicates .f

a mark and the absenceof an impulse indicates a space Five signals will give a total of 32 combinations and, therefore, 426 of these 32 combinations may be used as the English alphabet.

Since the trigger circuit YI3 controls the phase reversing network l2, a 180 degree phase reversal occurs in the radio frequency carrier across tank ,circuit 21 whenever a negative pulse occurs at point 43. Thus the "mark-space information has been converted into a series of phase reversals of transmitted pulses. The correspondence is between"mar'k and a reversal of the radio frequency carrier, and ""space and a lack of reversal, as opposed to the conventional polar system 'in which a r"r`nark`is represented by one phase and a space by the opposite phase. rIhis requires the transmission o'f'one more vout put pulse than'the 'numberof marks and spaces since the firstpulse vacts as a reference for de'- Vteimining whether or not a reversal has oc- `3. The incoming signal is received by an antenna, not shown,`and"furnished to' a mixer 44 which als'o receives a signalfrom a mixing oscillator "46. An'intermediate frequency '-amplier 41 receivesthe 'output of mixer and passes i'tto aphase' detector 48.r A'local oscillator 49 'oscillates at substantiallythe"center frequency of the intermediate frequency output of the amplifier 41 and for illustrative purposes, |00

kc. has been used as a possible frequency. A(A

frequency doubler 5| receives a portion .of the amplifier 41 output. An output fromioscillator 49 is furnished to a secondfrequency-doubler 5.2. whih. intern feeds` 'afninetvslesree phase output will be obtained from the phase detector 54. The output of phase detector 54 is fed to the frequency controlling element 56 causing the frequency "of the os'cillatortobe shifted through a range ofvalues including the desired frequency where a phase lock will'beobtained.

' The envelope nof the transmitted pulses will thus be reproduced'at the output of phase detector 48. The `Ypolarity ofthe output Y pulses will be positive 'when the signal Yfrom .oscillator 49 is in phase with the "incoming "signal and the polarity will be vn'eg'ativewh'en the signals are Aout of phase.

A pair of'diode "rectiers 451"and58'receive the output from 'phase detector '48. "The .'Iplate 59 of -tube '-51V andthe cathode J61 of tube 58 are connected `togetlienandthus, 'tube 51 passes thefpositive "pulses and'tub'e "58 passes the negative pulses.

As bestshewnin'Figfg, a"D.iC.'ampli'fier 62 receives Athe "positive pulses from ntube '51 and amplies themand inverts them vto negative pulses. A pairl of :D5-C. ampliers"'63"and"64 receive the Anegative pulses from tube "58 and amplify them; Itis to'be noted :that 'the' polarity of the output-of `arnplirleri6`4 is negative 'because ltube B3 changed the 4'negative pulses to 'jpo'sitive ones and 'tubei6`4'ch'anged'them back 'to negative. v-The gain of amplierii! is of"'the"same'order las the total fga'in throu-ghampliers 63"and '64. A@triggercircuit-tais controlledby the "outputs from amplifiers 62 andf`9`4withicontrol grid '61 of `-tube #68 `"receiving the output ofv lamplifier Athey bias-*the tubesiffiand 1|, respectively, past `A"fullwaverectifier 12fiscouplebl to =the-'out put of the trigger circuit 66 and gives afposit'ive pulse `4every "time conduction V'changes the trigger circuit. Thus the data delivered to 'the transmitter "trigger "circuit 1.3 is 'reproduced by 'the'fullwave rectifier 12. AIhe'vdatav is then .de-

transmittedI messagell' A ,4.1.1 alternative' ,mbdimenwf the #principles of this invention for the reception of a trans,-

coded bya second teletype`- machine Vinto -the is blocked off during fmission'suenas is emitted'fby .the transmitter. of Fig-"1. isshown in'Fig. 5.V

Here the '0'kc. intermediate frequency waveis .rectifiedv by envelope Yfrectifier 'I3l which' produces a positive pulse onvreceiptof an intermediate frequency pulse of either-phase. `These pulsesv are applied to a fiip-op circuit 14 which produces av pushpull` square-wave voltage' in synchronism with the received pulses. Thiscsquare wave voltage is applied as blocking voltage to a pair of keyed amplifiers 16 and 11 so that Aoneamplifier the reception of onepulse and the other is' blocked ,off during the reception of the next pulse. Both keyedv amplifiers receive the 100 kc.V intermediate frequency signal and the plate circuit of each is connected to a resonatingcircuit-*IB andl of Ylow decrement.

Hence, there remains in the Vresonator ofthe tube which is blocked off during the reception of a pulse an appreciable oscillation which was Ainduced yin this resonator during the reception vof the previous pulse. The phase of this remnant oscillation is compared with that of the oscilla- `tion from'the current pulse in' the otherresonator by phasedetectingrectifier 8l so that the output of this rectifier is positive whenever two successive pulses are received in like phase and negative whenever successive pulses are received in unlike phase. The output of this phase detector is then treated just like the output of the phase detector 48 in Fig. 3. Y

In operation, the message to be transmitted is furnished to the encoding information source I8 which changes it into mark-space intelligence. Fig. 6 gives an example of the form of the information to be furnished to the trigger circuit I3. As shown in Fig. 7 each mark causes the modulated carrier wave to reverse phase by 180 degrees. Thus, between pulse A and B a reversal occurred because of the mark H furnished to trigger circuit I3. A phase reversal occurred between pulses B and C because of the mar I. No change occurred between pulse C and D because there was no mark.

The wave radiated from antenna I6 will be of the form shown in Fig. 7.

The phase detector 48 will compare the incoming signal with the local oscillator 49 output and will give an output of positive and negative pulses which have theshape of the envelope of the modulation on the carrier. For illustrative purposes, the phase detector output has been shown in the. form of peaked pulses. The polarity of the pulse is the important controlling factor and not the wave shape.

Figure 8 illustrates the phase detector 48 output when the oscillator 49 output is in phase with pulse A of the incoming signal. Pulse K will be positive, pulse L negative because of the phase reversal between pulse A and B of the incoming signal and so on.

If on the other hand, the local oscillator 49 locks in phase with the incoming signal so that pulse A is 180 degrees out of phase with the oscillator output, a negative pulse will be obtained and the output will look like Fig. 9. It is to be noted that the only difference between the pulses of Fig. 8 and the pulses of Fig. 9 is that the polarity of each one is reversed.

The output of full-wave rectifier 12 is shown in Fig. 9 and is the same for the conditions shown in either Fig. 7 or Fig. 8. This is true because the full wave rectifier gives a positive output each time va change in signal is applied to phase detector 48.

Thefoutput'of the full-wave rectifier lis decoded in a teleprinter or other .well known 'decoder and the original message has been transmitted. y Y

.Although-this invention-has been described with respect to preferred embodiments thereof,

Yit is not to be so limited as'changes andmodifications may be made therein whichare Within the as defined by the appended `phase vector representing the receivedsignal, a

phase detectorreceiving .the receivedsignal and .the outputV of said local oscillator to compare them and give a positive signal when they are in'phase and a negativesignal when they are out of phase, a pair of rectiiiers receiving the output of said phase detector, and one ofthe rectiers passing the positive signals andthe other rectifier passing the: negative signals, a direct-current ampli.- fier receiving the positive output of the one rectifier to invert it to a second negative signal, a trigger circuit with its grids controlled by the first and second negative signals, and a full wave rectifier @coupled to said trigger circuit and giving data output.

2. In a polar transmission system, according to claim 1, a phase and frequency stabilizer for said local oscillator comprising, a first frequency doubler receiving an incoming signal, a second frequency doubler receiving an output from the local oscillator, a degree phase-shift network receiving the output of said second frequency doubler, a second phase detector receiving an output from the first frequency doubler and an output from the phase shifting network, the output of said second phase detector fed to phase and frequency control means on said local oscillator for maintaining the frequency of the signals received by said second phase detector in synchronism.

3. In a polar communication system wherein the radio frequency phase of a transmitted pulse is reversed with respect to that of the previous pulse in the presence of a signaling pulse, a receiver comprising, an envelope rectifier receiving the incoming signal, a trigger circuit triggered by the output from said envelope rectifier, a pair of keyed amplifiers receiving an output from said antenna, said trigger circuit controlling said amplifiers so that conduction ichanges from one to the other at each pulse of the received wave, a first tank circuit of low decrement connected to the output of one of the keyed amplifiers, a second tank circuit of low decrement connected to the output of the other keyed amplier, phase detecting means coupled to the first and second tank circuits to compare their phase and give a positive output when successive pulses are in phaseand a negative output when they are out of phase, a pair of rectifiers receiving the output from said phase detector and one rectifier passing the positive output and the second rectifier passing the negative output, a direct current amplifier receiving the positive output of the one rectifler to invert it to a negative output, a trigger circuit with its grid controlled by the output from said direct current amplifier and said second rectifier. respectively, and a full-wave merma@ mctienmnpled tasafdzrig'ger circuitrtorgvef-.output datastpulses.

f4. A :amant energy means .comprising. a. reference oscillator producing a signal :of thesame frequency. asfarreceived signal..r `a .phase .detector :comparingfthephase I.off thereceivedifsig- .nal :with :the iphasei of=thef.:o11tput fof rsaid :referfence; oscillator :togivegaizpositiye.outputfwhenfthe .signals-are in phasezand aznegative-sgnal-when they are out of phase, a direct current amplifier receiving said positive output and inverting-it to ehtanfa megaitivefzsignal,iafatrigger1 circuit.y receiv- :ing'inputs fromesaidildirecticurrent.-amplierand isa-id .phase detector. and :.full .wave -rectifying meansrconnecteditoaidttrigger circuit comproducevdaata .5. xAsreceiving lmeans. .comprising, an z envelope .rectifier receiver `receivingvan incoming signal. :arrstitrigger crcuitiproducinga square Wave in irrespcvnseftov aninputzreceixd from said .envelope rectifier, a^-pair of.l keyed: amplifiers `cormectedmo said triggercircuit and .alternately :keyed on and the incoming. signalwsupplied to sa-id fkeyed amplifiers, a first resonant @circuit of lowA decrement-connected;totheirstkeyed. amplifier, `a secnnd.resanantecircuitoflowfdecrementfconnented to the second eyedffamp'lier,fafpliase detector tuned circuits, a

yavsecond vtrigger :circuit connected .to said halffwaye 1*.ecti1r1fs-V 6. Areceivjnggsystem comprising, .a phase .detector, a local .oscillator supplying `an input lto said ,phase-detector, anfincoming signal -Supplied .tozsaid phaseadetector, a-i'pair of frectiers connectedvito saidigphasefdetectori-to `pass outputs of .Number Name `Date 1,559,642 Nyquist e-,mw ,N0v.. 3,4 1925 2,922,282 V,Bellescize .Al1g.,.15, ,19.33 .2,113,214 .Luck ,A1312 v5, 1938 ,2,491,810 .Guanella ,Dec. 20, 1949 2,509,066 ..Koch .May.23, ..1950 

